ON THE SPONTANEOUS CONFIGURATION OF FERROELECTRIC-FERROELASTIC MATERIALS
关于铁电铁弹材料的自然构形

The behavior of ferroelectric-ferroelastic materials depends upon their microstructures. Nonuniqueness of spontaneous deformations and directions of spontaneous polarization, and existence of various singular surfaces in such a material cause the spontaneous configuration of a ferroelectric-ferroelastic material to have an intricate structure. In this work, a nonconvex energy density of deformation gradients and of electric displacements is assumed for ferroelectricferroelastic single crystals. From an energetic point of view, necessary conditions for a stable spontaneous configuration are derived. It is concluded that the stable spontaneous configuration of a ferroelectric- ferroelastic polycrystalline material consist s of a coarse mixture of various ferroelectric domains. The volume fractions of the domains with the same spontaneous deformation gradient depend upon the orientations of the grain boundaries, the orientations of crystal lattices, and the twinning mode.